1. Field of the Invention
The present invention relates to lactam derivatives, methods for their production, and methods for their use.
2. Description of Related Art
The preparation of various reaction products of xcex5-caprolactam, formaldehyde, and hydroxyl-containing compounds is known: for example, N-[(isopentyloxy)methyl]caprolactam from V. A. Chauzov et al., Journal of General Chemistry of the USSR, 59 (1989) p. 425; and N-[(2,6-di-tert-butylphenoxy)methyl]caprolactam from DE-A 26 16 374. The preparation of N,N-linked bislactam compounds is described in DE-A 35 06 473; the preparation of N-methylolcaprolactam in DE-A 37 00 451.
Melamine resins made from melamine and formaldehyde are general knowledge and are described, for example, in xe2x80x9cKunststoff-Handbuchxe2x80x9d, 2nd edition, 1988, vol. 10, pp. 41 to 49. Melamine-formaldehyde precondensates whose methylol groups are unetherified or etherified in part with alcohols such as methanol are generally prepared in an aqueous medium and also commercialized in aqueous form. They are used preferably for impregnating paper webs, especially decorative paper webs, which are subsequently employed to produce laminates, decoratively coated chipboard panels or compression-formed laminates. For this purpose, the paper webs are impregnated to a defined resin content in the aqueous impregnating-resin solutions, to which a curing agent may have been added, and are dried to a defined residual moisture content at temperatures from 120 to 200xc2x0 C. The fabric or paper webs treated in this way are pressed onto woodbase materials or a stack of resinated papers employing pressures of from 0.8 to 12 MPa (from 8 to 120 bar) and temperatures of from 100 to 180 C.
In this way, decorative laminates and coated woodbase materials are obtained which are employed primarily in interior furnishing, for producing furniture or as a floor covering, to cite but a few of the possible applications.
Melamine resins are prepared by condensing formaldehyde with melamine, the condensation being continued only to a point at which the reaction products are still soluble and meltable. When this point is reached, the condensation is terminated by cooling and by establishing a weakly alkaline pH. This gives products which have not been fully condensed, these products also being termed melamine resin precondensates and being used in the form of their aqueous solutions, for example, as impregnating resins. It is also now possible to replace up to 20% of the melamine by one or more other amino resin formers, examples being guanamines (e.g., acetoguanamine, benzoguanamine and caprinoguan-amine), dicyandiamide, urea and thiourea, and also cyclic ureas (e.g. ethylene- and propyleneurea).
When the fabric or paper webs which have been impregnated with impregnating resin and dried are pressed into laminates, curing takes place as a result of thorough crosslinking of the condensate. When coating woodbase materials in particular it is important that the melamine resins employed are elasticized with modifiers in order to prevent subsequent cracking of the coated surface. The impregnating resin can be etherified in part with lower alcohols or modified with modifiers such as polyhydric alcohols, carboxamides, glycols, sulfonamides and sugars, and can also be catalyzed with acidic inorganic or organic salts.
In the art, diethylene glycol and xcex5-caprolactam are frequently employed as modifiers. They give the cured films the necessary elasticity coupled with good surface properties, such as low soiling tendency, low sensitivity to steam and boiling water, low yellowing propensity, high scratch resistance, low propensity to cracking, and good postforming properties.
A disadvantage of these modifiers is their relatively high volatility. When papers impregnated with resins modified in this way are dried, some of the modifiers present are given off into the air. This problem is exacerbated when the dryer temperatures are raised owing to higher machine speeds. In accordance with the art, customary drying temperatures are from 140 to 200xc2x0 C. In order to avoid these emissions, it is therefore necessary with prior art resins to make considerable investment in filter units and/or post-combustion units, in general.
This problem applies in particular to xcex5-caprolactam, for which a MAC level of 5 mg/m3 has been laid down.
It is therefore an object of the present invention to provide modifiers for impregnating resins and resins modified therewith which when used in the coating of woodbase materials result in minimal amounts of organic compounds being emitted. In addition, the coatings produced with these resins should be elastic and should not tend to crack.
It is also an object of the invention to provide methods of making and using such modifiers.
In accordance with these and other objectives, there has been provided in accordance with the present invention an N-alkoxymethyllactam of the formula VI 
where X is xe2x80x94(OCH2-CR1H)mxe2x80x94OR2, and R1 and R2 in each case independently of one another are hydrogen or a linear or branched alkyl radical having 1 to 6 carbon atoms,
l is 3to 12and m is 1 to 20,
or where X is xe2x80x94Oxe2x80x94(CH2)nxe2x80x94OR3, and R3 is hydrogen or a linear or branched alkyl radical having 1 to 6 carbon atoms and n is 2 to 8, obtained by reacting a lactam of the formula I 
where 1 is as defined above, with formaldehyde and hydroxyl-containing compounds selected from diols and/or diol monoethers of formula II
H(xe2x80x94Oxe2x80x94CH2-CR1H)mxe2x80x94OR 2xe2x80x83xe2x80x83(II),
where R1, R2 and m are as defined above, and diols and/or diol monoethers of formula III
HOxe2x80x94(CH2)nxe2x80x94OR3xe2x80x83xe2x80x83(III)
where R3 and n are as defined above, wherein the reaction comprises reacting from 1 to 4 mol of formaldehyde and from 0.5 to 6 mol of the hydroxy containing compound one another per mole of the lactam of the formula I.
In accordance with these and other objectives, there has also been provided a is a mixture comprising one or more N-alkoxymethyllactams of the formula VI 
and one or more N-methylollactams of the formula IV 
and one or more N, Nxe2x80x2-methylenebislactams of the formula V 
in which X is xe2x80x94(OCH2xe2x80x94CR1H)mxe2x80x94OR2 or xe2x80x94Oxe2x80x94(CH2)nxe2x80x94OR3, R1, R2 and R3 independently of one another are hydrogen or a linear or branched alkyl radical having 1 to 6 carbon atoms and l is an integer from 3 to 12, m is 1 to 20, and n is 2 to 8.
In accordance with these and other objectives, there has been provided a melamine impregnating resin formulation comprising or prepared from an N-alkoxymethyllactam of the formula VI as modifier in a proportion by mass of from 1 to 20%, based on the mass of the solid melamine resin.
In accordance with these and other objectives, there has been provided a melamine impregnating resin formulation comprising or prepared from and a mixture as discussed above as modifier in a proportion by mass of from 1 to 20%, based on the mass of the solid melamine resin.